--
-- This file is part of TALER
-- Copyright (C) 2014--2022 Taler Systems SA
--
-- TALER is free software; you can redistribute it and/or modify it under the
-- terms of the GNU General Public License as published by the Free Software
-- Foundation; either version 3, or (at your option) any later version.
--
-- TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-- WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-- A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License along with
-- TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
--


CREATE OR REPLACE FUNCTION exchange_do_history_request(
  IN in_reserve_pub BYTEA,
  IN in_reserve_sig BYTEA,
  IN in_request_timestamp INT8,
  IN in_history_fee_val INT8,
  IN in_history_fee_frac INT4,
  OUT out_balance_ok BOOLEAN,
  OUT out_idempotent BOOLEAN)
LANGUAGE plpgsql
AS $$
BEGIN

  -- Insert and check for idempotency.
  INSERT INTO exchange.history_requests
  (reserve_pub
  ,request_timestamp
  ,reserve_sig
  ,history_fee_val
  ,history_fee_frac)
  VALUES
  (in_reserve_pub
  ,in_request_timestamp
  ,in_reserve_sig
  ,in_history_fee_val
  ,in_history_fee_frac)
  ON CONFLICT DO NOTHING;

  IF NOT FOUND
  THEN
    out_balance_ok=TRUE;
    out_idempotent=TRUE;
    RETURN;
  END IF;

  out_idempotent=FALSE;

  -- Update reserve balance.
  UPDATE exchange.reserves
   SET
    current_balance_frac=current_balance_frac-in_history_fee_frac
       + CASE
         WHEN current_balance_frac < in_history_fee_frac
         THEN 100000000
         ELSE 0
         END,
    current_balance_val=current_balance_val-in_history_fee_val
       - CASE
         WHEN current_balance_frac < in_history_fee_frac
         THEN 1
         ELSE 0
         END
  WHERE
    reserve_pub=in_reserve_pub
    AND ( (current_balance_val > in_history_fee_val) OR
          ( (current_balance_frac >= in_history_fee_frac) AND
            (current_balance_val >= in_history_fee_val) ) );

  IF NOT FOUND
  THEN
    -- Either reserve does not exist, or balance insufficient.
    -- Both we treat the same here as balance insufficient.
    out_balance_ok=FALSE;
    RETURN;
  END IF;

  out_balance_ok=TRUE;
END $$;